High resistance rotor



March Z6, 1963 R. J. BoLEs HIGH RESISTANCE RoToR 2 Sheets-Sheet 1 Filed Dec. 29, 1959 F IG. 8

NVENTOR.

RICHARD J. BOLES BY Jil-Mw l ATTOR N EY March 26, 1963 R. J. BoLEs HIGH RESISTANCE RoToR 2 Sheets-Sheet 2 Filed Dec. 29, 1959 RICHARD J. BOLES BY K (5.74%

ATTORNEY 3,083,3i3 HGH RESISTANCE, RTOR Richard J. Boles, Pittsfield, Mass., assigner to General Electric Company, a corporation of New York Filed Dec. 29, 1959, Ser. No. 862,622 5 Claims. (Cl. 31o-212) The invention described herein relates to dynamoelectric machines and more particularly to an improved winding design adapted vfor use in high resistance rotors.

The copending patent application of E. R. Summers and G. M. Rosenfberry, Serial No. 857, iiled January 6, 1960, and assigned to the same assignee as the present invention, discloses in detail the problems associated with casting a winding in high resistance rotors and provides a new casting process and winding which eliminate dithculties heretofore encountered in rotors of this type. A discussion in the copending application of the inadequacies of prior art casting processes and the problems presented in obtaining sound windings in high resistance rotors show that the diiculties primarily are caused by the shrinkage characteristics of aluminum and the rapid rate of freezing during casting.

In some instances, it has been found that the punchings in a cast high resistance rotor delaminate or separate near the ends of the rotor and particularly in those cases where the winding design is of zigzag conguration. This unwanted action is attributable to the fact that the axial section of each cast conductor bar in the zigzag winding is alternately positioned near the rotor bore and near the rotor surface. Since these inner and outer axial sections are located in the same relative position in each conductor between the end rings, it the winding could be removed `from the laminated core, it would be seen that a series of circular grooves appear circumtfeientially around the winding` and repeat themselves uniformly along the length of the rotor. The conductor bars are separated from each other of course, and the grooves 'will appear at every point along the rotor length where the inner axial conductor sections are positioned near the bore.` When an aluminum winding of this design is cast and freezes, substantial shrinkage occurs in the cast material so that the conductor bars are placed in tension and the end rings shrink a corresponding amount inwardly. This action causes the diameter of the end rings to close and exert a radially inward force on the bars which results in establishment of a fulcrum point at each inner axial section about which the ring moves. Such movement pulls the outer axial sections towards the ends of the rotor and is permitted to do so because a suiicient restraining force is not available to counteract the inward torce exerted by the end rings, Stated diierently, the grooves established between the inner axial section and the outer peripheral surface of the winding are of sufficient radial depth that no restraining force is available to resist the forces exerted on the winding by the end rings. As one might expect, the forces established by end ring contraction have their maximum eiect near the ends of the rotor with little effect at the center. As a result, since the aluminum conforms very closely to the iron of the punchings, and since the winding grooves actually are occupied by the iron of the punchings, the end ring forces cause the punchings to separate or delaminate near the ends of the rotor. r Y

It is evident therefore that the need exists for a slot arrangement for the cast winding which will be efective in minimizing or eliminating the adverse effects caused by Patented Mar. 2d, 1963 Nie 2 shrinkage of the end ring in the manner described above.

Accordingly, the primary object of my invention is to provide a winding design in the rotor which will prevent delamination of the punchings after casting the winding in the rotor slots.

. In carrying out my invention in one form I select laminations having different slot designs and alternately stack like slotted lam-inations in sections to form a rotor core. The location and coniigtuation of slots in the different section laminations are chosen such that when the rotor is assembled and a winding cast therein, each of lthe longitudinal conductors between the end rings will be of zigzag design. The axial portions of the conductor bars along the rotor length are shifted alternately from a position near the bore to a position near the rotor surface in a staggered pattern. To impart rigidity to the core for preventing the end rings from causing delamination in the punching stack, the zigzag arrangement in every other conductor slot is staggered or displaced from the zigzag ,arrangement in the next conductor slot in the rotor. It will be apparent to those skilled in the art that many designs and configurations of slots may be incorporated in each section of laminations for achieving a zigzag arrangement and wherein sections in one conductor slot are displaced 180 lfrom those in the next adjacent slot.

While Vthe specification concludes with clai-ms particularly pointing out and distinctly claiming the subject matter which I regard as my invention, it is believed the invention will -be better understood from the following description taken in connection with the accompanying drawings in which:

FiGURE l is a View in elevation of a high resistance rotor including fan blades and end rings positioned on opposite ends thereof;

FIGURE 2 is a view in elevation of a part of a lamination used in constructing the rotor of FIGURE l;

FIGURE 3 is a view similiar to FIGURE 2 except that the slots in the lamination are of a diierent design;

FIGURE 4 illustrates the lamination of the same design as in FIGURE 2 except that the keyway therein is displaced M2 slot pitch from the keywiay in FIGURE 2;

FIGURE 5 is a view in elevation illustrating the design of the slots when thelaminations are assembled;

FIGURE 6 is an isometric cross sectional View taken on lines 6-6 of FIGURE 5;

g FIGURE 7 is a view in elevation of a conductor positioned in the zigzag slots extending from one end of the rotor to the other; and

FIGURE 8 is a view illustrating the contigui-ation of the conductor in the slots on either side of slots containing part of the conductor winding shown in FIGURE 7.

Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the Vseveral views there is shown in FIGURE 1 a rotor core 10' comprising a plurality of laminations 12 containing. a high resistance winding (not shown) having end ringsjli and fan blades 16 integrally connected therewith.

The laminations used in forming the rotor of FIGURE lare illustrated in FIGURES 2, 3, and 4 and reference to FIGURE 2 will show a lamination 20 equipped with a central bore 21 having a keyway 22 punched therein. Inner and outer concentric rows of conductor slots 26 and 28 are disposed around the lamination with an equal number of slots in both rows. As shown, the keyway 22 is radially aligned with an inner slot 2.8 and with a blank portion of the lamination between slots 26 adjacent the punching surface.

' design in sections.

The lamination 30 illustrated in FIGURE 3 likewise has a central bore 2l and a keyway Z2 and inner and outer diameters of the same dimension as the lamination shown in FIGURE 2. The slots 32 however are of different design and as illustrated, are of a length sumcient to bridge the complete radial distance covered by the slots 2.6 and 28 in punching 2th The lamination 40 of FIGURE 4 is exactly the same as the lamination 20 shown in FIGURE 2, except that the keyway '22 is radially aligned with a slot 26 positioned in the outer row of slots in the lamination. Displacement of the keyway "1/2 slot pitch in this lamination permits obtaining an out of phase relationship in the zigzag conductors in adjacent slots as more fully described hereinafter.

Y The function of the laminations shown in FIGURES 2, 3 and 4 is to provide a zigzag `design in the conductor slots extending the complete length of the rotor. This is accomplished by stacking laminations of the same slot The sections are then assembled on an arbor or other device in a manner to have the slots in various sections in alignment for receiving cast material when it is poured or otherwise cast to form the winding. FIGURE 5 illustrates the slot alignment of sections while FIGURE 6 shows the disposition of a winding in the slots. Since a relatively large amount of aluminum is necessary in high resistance windings for providing the required thermal capacity and for furnishing a large surface area for transmitting heat to the iron core, it will be apparent that the size of the conductor bars and the particular design of the slots may be varied merely by changing the slot configuration in each punching.

As illustrated in FIGURE 6, the first section comprising laminations Btl of FIGURE 3 having aligned slots 32 provide a relatively long radial slot 42 which communicate with aligned slots 26 in laminations 2t) of FIGURE 2 to furnish the outer axial slot portion 44. In order to accomplish a zigzag design, a second section of laminations 30 are then stacked next to laminations 20. The axially aligned slots 32 form the radial slot portion 46 which connects with axially yaligned slots 28 in laminations 4t) of FIGURE 4 to provide the inner axial slot portion `48. This pattern repeats itself throughout the length of the rotor.

It therefore will be seen that by assembling the sections of the laminations in the manner described above the communicating openings in the slots of each section will be such as to provide a zigzag .arrangement of the type illustrated in FIGURE 6i. In order to provide rigidity to the rotor, it is desirable to alternate the position of each inner and outer axial portion 44 and 48 in adjacent conductor slots so that they are 180 out of phase. In other words, the outer -axial portion 44 in a rst conductor slot will be positioned radially inwardly in the next conductor slot so that it is near to the bore, and the inne-r axial portion 48 inthe first 4conductor slot will be located near the rotor surface in the next conductor slot. This alternating arrangement then occurs in each succeeding conductor slot circumferentially Iaround the rotor core. The staggered relationship is achieved merely by having laminations 20 and` 40 in each section displaced from each other by 1/2 slot pitch. This is accomplished by having the keyway 22 in each of punchings 20 and 40 displaced I1/2 slot pitch with respect to each other. Obviously, instead of having an inventory of two separate types of punchings, each having individual keyways, both keyways could be punched in the same punchings but respectively aligned with the inner and outer slots.

When a winding is cast in the conductor slots thus provided in the rotor of FIGURE 6, it will assume the path shown therein and will provide cast conductor bars of the type shown in FIGURES 7 and 8. These views show the` designof winding conductors in adjacent conductor slots. As shown, each of these sections of conductor bars 50 and 52 have end rings 14 positioned on opposite ends thereof with the conductor section being positioned therebetween. Each outer axial section 54 is displaced 180 from an inner axial section 56 which would b e positioned in the next adjacent slot.

The effect produced by the above construction is that from a structural standpoint the rotor acts as though a plurality of uninterrupted axial bars were disposed in the slots of the rotor. This results from the fact that the zigzag portions of each conductor slot are displaced from the next adjacent section and accordingly provides rigidity throughout the rotor. Therefore, when the winding is cast, the restraining force furnished bythe displaced outer and inner axial portions, is greater than the inward forces exerted by the end rings when the 4material therein shrinks. This eliminates the unwanted delamination of the punchings near the ends of the rotor as is prevalent in the prior art designs. The arrows in FIGURES 7 and 8` show the direction of end ring movement in prior art designs which cause those portions of the winding indicated at 6d to separate from one another, and since the aluminum in this part of the winding is molded around the inner surface of the laminations, the laminations accordingly were pulled apart thus causing a gap in the rotor surface. When rotors of the design described in this application are cast, the end ring again shrinks inwardly and exerts the same forces as before, but since the section indicated as 54 is now positioned in every other slot trom those which contain the sections indicated 56, sufficient strength is provided for counteracting the forces exerted by the end rings during shrinkage.

The above description has been directed to a construction disclosing different types of slots but it will be apparent that many modifications and variations may be made to the construction disclosed in order to provide a zigzag arrangement of slots in the rotor. Although only two different types of punchings have been shown, it will be evident that an additional number may be used to obtain a construction which will perform the same function as that disclosed herein. Moreover, the winding may be cast in accordance with the teachings in the above copcnding application which utilizes vent openings for venting air to the bore and/ or feeding molten aluminum to the winding. The construction of this application also has been cast with static casting methods to produce sound windings wherein the parts are completely formed. It therefore is to be understood that within the scope of the appended claims the invention may be practiced other than as specifically described.

What I claim as new and desire to secure. by Letters Patent of the United States is:

l. A high resistance rotor comprising laminations assembled to form a rotor core, a winding in said core integrally connected with fan blades and end rings on 0pposite ends thereof, said winding comprising a longitudinally extending conductor in each conductor slot spanning the core length, each conductor being arranged to alternate in a direction toward and away from the rotor bore, and every other conductor placed in an out of phase relationship with the conductor in the next adjacent slot.

2. A high resistance rotor comprising laminations assembled to form a rotor core, a winding in slots provided in said core and integrally connected with fan blades and end rings on opposite ends thereof, said winding comprising a conductor in each slot having portions alternately directed inwardly and outwardly from the rotor bore in a zigzag pattern, said conductor portions further being displaced 180 from each other in each succeeding slot around the rotor core.`

3. The combination according to claim 2 wherein the zigzag pattern is uniform throughout the core length.

4. The combination according to claim 2. wherein the zigzag pattern is non-uniform throughout the core length.

5. A high resistance rotor comprising laminations assembled to form a rotor core, a winding in slots provided in said core and integrally connected with fan blades and 5 6 end rings on opposite ends thereof, a conductor in each cent slot, thereby Placing adjacent COIldUCtOIS 180 Out slot extending the length of the core, each said conductor Of phase around the Core.

including axial portions alternately positioned near the References Cited in the-file of this patent bore of the rotor and near the rotor surface, the ends of said portions being bridged by radially extending bars, 5 UNITED STATES PATENTS and said end rings integrally connected to opposite. ends 2,196,059 COX APL 2, 1940 of each conductor, the conductors in adjacent slots being FOREIGN PATENTS disposed such that the axial portions in one slot are dis- 690,541 Germany APL 27I 1940 placed in radial position with respect to those in an adja- 503.288 Canada May 25, 1954 

5. A HIGH RESISTANCE ROTOR COMPRISING LAMINATIONS ASSEMBLED TO FORM A ROTOR CORE, A WINDING IN SLOTS PROVIDED IN SAID CORE AND INTEGRALLY CONNECTED WITH FAN BLADES AND END RINGS ON OPPOSITE ENDS THEREOF, A CONDUCTOR IN EACH SLOT EXTENDING THE LENGTH OF THE CORE, EACH SAID CONDUCTOR INCLUDING AXIAL PORTIONS ALTERNATELY POSITIONED NEAR THE BORE OF THE ROTOR AND NEAR THE ROTOR SURFACE, THE ENDS OF SAID PORTIONS BEING BRIDGED BY RADIALLY EXTENDING BARS, AND SAID END RINGS INTEGRALLY CONNECTED TO OPPOSITE ENDS OF EACH CONDUCTOR, THE CONDUCTORS IN ADJACENT SLOTS BEING DISPOSED SUCH THAT THE AXIAL PORTIONS IN ONE SLOT ARE DISPLACED IN RADIAL POSITION WITH RESPECT TO THOSE IN AN ADJACENT SLOT, THEREBY PLACING ADJACENT CONDUCTORS 180* OUT OF PHASE AROUND THE CORE. 